1. Field of the Invention
The present invention relates to a microstrip line antenna, and more specifically, to a novel construction of a circularly polarized microstrip line antenna.
2. Description of the Prior Art
Conventionally, there has been presented a circularly polarized microstrip line antenna of a type as shown in FIG. 1, which is of a travelling-wave antenna including a dielectric substrate 1, a ground plate 2 uniformly formed on the reverse surface of the dielectric substrate 1, and a strip conductor 3 formed by periodical folding or bending so as to be further provided thereon as shown, and which has already been proposed by the present inventors.
However, since the known antennas of the above described type are all travelling-wave antennas which are each formed by periodically folding a single continuous strip conductor, upon variation of the frequency so as to be higher or lower than the working central frequency, the main beam direction scans along the longitudinal direction of the dielectric base plate 1. Therefore, in the application to the transmission or reception with respect to one predetermined direction, there is such a disadvantage that the frequency band-width is undesirably limited upon the consideration of the influence caused by the scanning.
It is an object of the present invention to provide an improved circularly polarized microstrip line antenna of a new type.